Fluid control system for a rotational atherectomy device

ABSTRACT

A method for controlling fluid flow in a rotational atherectomy device. A source of fluid is provided through a pump to the rotational atherectomy device, wherein the pump maintains the fluid flow at a minimal rate during a time period when a drive shaft of the device is not rotating. A first control is activated to increase a rate of the fluid flow and second control is activated to initiate a rotation of the drive shaft during another time period when the fluid flow is at the increased rate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to devices and methods forremoving tissue from body passageways and, more particularly, to acontrol system for a rotational and or orbital angioplasty device.

2. Brief Description of Related Developments

There are a number of different techniques and devices which have beendeveloped for use in removal and/or repair of arteries and other similarbody passages. One objective of some of the aforementioned devices andtechniques is removal of atherosclerotic plaques from patient'sarteries. Atherosclerosis is characterized by buildup of fatty deposits(atheromas) in the intimal layer (under the endothelium) of a patient'sblood vessels. Very often over time, what initially is deposited asrelatively soft, cholesterol-rich atheromatous material hardens into acalcified atherosclerotic plaque. Such atheromas restrict the flow ofblood, and therefore often are referred to as stenotic lesions orstenoses. If left untreated, such stenoses can cause angina,hypertension, myocardial infarction, strokes and the like.

Rotational angioplasty procedures are a common technique for removingsuch stenotic material. Such procedures are used most frequently tocommence the opening of calcified lesions in coronary arteries. Oftenthe rotational angioplasty procedure is not used alone, but is followedby a balloon angioplasty procedure. This, in turn, may frequently befollowed by placement of a stent to assist in keeping the artery open.For noncalcified lesions, balloon angioplasty most often is used aloneto open the artery, with stents often placed to maintain the openedartery. Studies have shown, however, that a significant percentage ofpatients who have undergone balloon angioplasty and had a stent placedin an artery experience in-stent restenosis (i.e., blockage of thestent) which most frequently develops over a period of time as a resultof excessive growth of scar tissue within the stent. Rotationalangioplasty devices were utilized in removing the excessive scar tissuefrom the stents and, thereby were useful in providing assistance inrestoring the patency of the arteries.

It should be understood that rotational angioplasty devices androtational angioplasty procedures are often referred to as rotationalatherectomy devices and rotational atherectomy procedures. These termsmay be used interchangeably herein.

One example of a rotational angioplasty device is shown in U.S. Pat. No.4,990,134 (issued to Auth), wherein a front or distal portion of a burris covered with an abrasive cutting material such as diamond particles.The diamond coated burr is mounted at the distal end of a flexible driveshaft. The burr is rotated at high speeds (typically, e.g., in the rangeof about 140,000-180,000 rpm) while it is advanced across the stenosis.The burr has a solid cross-section and thus, as the burr is removingstenotic tissue, it blocks blood flow through the artery. Once the burrhas been advanced across the stenosis, the artery will have been openedto a diameter equal to or only slightly larger than the maximum outerdiameter of the burr. A series of different size burrs may be utilizedto open the artery to a desired diameter. U.S. Pat. No. 5,897,566(issued to Shturman) shows another rotational angioplasty device havinga drive shaft made from helically wound wires. A section of the driveshaft has an enlarged diameter. In one embodiment at least a front ordistal segment of this enlarged diameter section is covered with anabrasive material to define an abrasive segment of the drive shaft. Theenlarged diameter section is hollow. This Shturman Device of the '566patent is capable of opening an artery only to a diameter about equal tothe maximum diameter of the enlarged diameter section of the driveshaft, thereby providing results similar to the Auth Device of the '134patent. The Shturman Device of the '566 patent possesses certainadvantages over the Auth Device of the '134 patent because it is moreflexible. Another example of a rotational angioplasty device is providedin U.S. Pat. No. 6,132,444 (issued to Shturman et al.) describes arotational atherectomy device having a flexible, elongated, rotatabledrive shaft with an eccentric enlarged diameter section. At least partof the eccentric enlarged diameter section has a tissue removing surfacewith an abrasive surface to define a tissue removing segment of thedrive shaft. When placed within an artery against stenotic tissue androtated at sufficiently high speeds (e.g. in the range of about 40,000rpm to about 200,000 rpm) the eccentric nature of the enlarged diametersection of the drive shaft causes such section to rotate in such afashion as to open the stenotic lesion to a diameter substantiallylarger than the maximum diameter of the enlarged diameter section.Preferably the eccentric enlarged diameter section of the drive shafthas a center of mass spaced radially from the rotational axis of thedrive shaft, facilitating the ability of the device to open the stenoticlesion to a diameter substantially larger than the maximum diameter ofthe enlarged diameter section. A drive shaft having an eccentricenlarged diameter tissue removal section with a diameter of not morethan 2 mm is capable of opening stenotic lesions to a diameter equal tothe original diameter of the coronary arteries (i.e., to a diameter ofmore than 3 mm) so that in a significant percentage of cases balloonangioplasty may not be needed to complete the procedure. The device isparticularly useful for cleaning out partially blocked stents.

U.S. Pat. No. 5,314,407 to Auth, which is incorporated herein byreference in its entirety, shows the details of a type of an advancer(handle) that may be used in conjunction with rotational atherectomydevices of the type described in Auth '134 patent and Shturman '566 and'444 patents. A handle of the type shown in Auth '407 patent has beencommercialized by Heart Technology, Inc. (Redmond, Wash.), now owned byBoston Scientific Corporation (Natick, Mass.), in the rotationalatherectomy (angioplasty) device sold under the trademark Rotablator.®.

FIG. 1 is an illustration of a rotational angioplasty system 100 of theprior art. As shown in FIG. 1, the prior art system comprises arotational angioplasty device 104, a fluid supply 106, a gas supply 108,a controller 102 and a foot pedal device 110.

The rotational angioplasty device 104 comprises an advancer assembly 134that is located within a body or handle 136. A gas driven turbine (notshown) is located within the advancer assembly 134 and rotates aflexible, hollow drive shaft 138. An ablative, diamond coated burr 140is attached at the distal end of the flexible drive shaft 138. Theflexible drive shaft 138 together with the burr 140 may be rotated overa guide wire 141.

As shown in FIG. 1, a flexible sheath 142 extends distally from thehandle 136 and surrounds the flexible drive shaft 138 substantiallyalong its entire length.

The advancer assembly 134 also carries a water (saline) pump (not.shown). This water pump is located distally to the gas turbine and has ashaft that is connected to the turbine shaft. The output of the fluidpump is in fluid connection with the lumen formed between the flexibledrive shaft 138 and the flexible sheath 142.

The rotational angioplasty system 100 shown in FIG. 1 includes aninfusion bag 128 to administer a saline solution. The saline bag 128 ispressurized with a pressure cuff 129 to ensure a steady supply of salineto the water pump within the advancer assembly 134 and around the driveshaft 138. The rotation of the gas turbine rotates the fluid pump andincreases the fluid flow rate in a lumen between the flexible driveshaft 138 and the sheath 142. The fluid flow rate in this system dependson the rotational speed of the gas turbine. Thus, the fluid accelerationin the lumen between the drive shaft 138 and the sheath 142 can onlytake place simultaneously with the increase in rotational speed of thegas turbine, and the system can not increase the fluid flow rate in thelumen between the drive shaft 138 and the sheath 142 without increasingthe rotational speed of the gas turbine.

A certain amount of static pressure must be applied and maintainedagainst the saline bag 128 in order to provide an adequate fluid flowrate in the lumen between the drive shaft 138 and the sheath 142. Thisrequires repeated repressurization of the pressure cuff 129 disposedaround the saline bag 128.

The controller 102 has a front panel 112 that includes a power switch113, a turbine control knob 114 (adjusts turbine pressure and RPMs), aturbine pressure gauge 115, a turbine (pneumatic) connector 116, aDynaGlide.™. (pneumatic) connector 117, and a pair of fiber opticconnectors 120. The front panel 112 also includes an event timer 122, aprocedure timer 123, and an optical tachometer display 124. The opticaltachometer provides or registers information about the rotational speedof the gas turbine of the rotational angioplasty device 104.

The foot pedal 110 is used as an on/off control for the gas turbine ofthe rotational angioplasty device 104. A DynaGlide.™. button 126 islocated on the right side of the foot pedal housing 132 and is used asan on/off control for the DynaGlide.™. mode of operation.

SUMMARY OF THE INVENTION

A method system and controller for controlling fluid flow in arotational atherectomy device. A source of fluid is provided through apump to the rotational atherectomy device, wherein the pump maintainsthe fluid flow at a minimal rate during a time period when a drive shaftof the device is not rotating. A first control is activated to increasea rate of the fluid flow and second control is activate to initiate arotation of the drive shaft during another time period when the fluidflow is at the increased rate.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and other features of the present invention areexplained in the following description, taken in connection with theaccompanying drawings, wherein:

FIG. 1 is a block diagram of a prior art rotational angioplasty device;

FIG. 2 is a perspective view of one embodiment of a rotationalangioplasty system incorporating features of the present invention;

FIG. 3 is a cross-sectional view of one embodiment of a roller pump;

FIG. 4 is a cross-sectional view of a roller pump in a closed position;

FIG. 5 is a cross-sectional view of one embodiment of a roller pump in aclosed position with fluid in the fluid line in a system incorporatingfeatures of the present invention;

FIG. 6 is a cross-sectional view of one embodiment of a fluid supplyline securing device incorporating features of the present invention;

FIG. 7 is a block diagram illustrating one embodiment of the functionalaspects of a controller for a system incorporating features of thepresent invention;

FIG. 8 is a timing diagram for pump and turbine activation periods inone embodiment of a system incorporating features of the presentinvention;

FIG. 9 is a timing diagram illustrating pump and turbine activationperiods in one embodiment of a system incorporating features of thepresent invention;

FIG. 10 is a timing diagram of pump and turbine activation periods inone embodiment of a system incorporating features of the presentinvention;

FIG. 11 is a timing diagram of pump and turbine activation periods inone embodiment of a system incorporating features of the presentinvention;

FIG. 12A is a schematic diagram of one embodiment of a timing circuit toproduce a delayed time period feature of a system incorporating featuresof the present invention;

FIG. 12B is a schematic diagram of one embodiment of a timing circuit toproduce a delayed time period in a system incorporating feature of thepresent invention;

FIGS. 13 and 14 are partial cross-sectional views of a pump cover sensorin embodiments of systems incorporating features of the presentinvention;

FIGS. 15 and 16 are partial cross-sectional views of embodiments offluid level detection systems for a system incorporating features of thepresent invention;

FIGS. 17 and 18 are embodiments of fluid level detection systems for asystem incorporating features of the present invention;

FIGS. 19 and 20 are embodiments of fluid level detection systems for asystem incorporating features of the present invention;

FIGS. 21 and 22 are embodiments of fluid level detection systems for asystem incorporating features of the present invention;

FIG. 23 is one embodiment of a fluid level detection system for a systemincorporating features of a present invention;

FIG. 24 is a block diagram of one embodiment of a control system for asystem incorporating features of the present invention;

FIG. 25 is a block diagram of one embodiment of a control system for asystem incorporating features of the present invention; and

FIG. 26 is a perspective view of one embodiment of a systemincorporating features of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 2, there is shown a perspective view of a rotationalangioplasty system 10 incorporating features of the present invention.Although the present invention will be described with reference to theembodiment(s) shown in the drawings, it should be understood that thepresent invention can be embodied in many alternate forms ofembodiments. In addition, any suitable size, shape or type of elementsor materials could be used.

As shown in FIG. 2, the system 10 generally comprises a rotationalangioplasty device (“RAD”) 20. The rotational angioplasty device 20 canalso comprise, or may be referred to as a rotational atherectomy device.As shown in FIG. 2, the RAD is generally coupled to a controller 60 anda fluid supply 50. The system 10 can also include an activation device30 and a gas supply system 40. Both the activation device 30 and gassupply system 40 can be coupled or connected to the controller 60. In analternate embodiment, the system 10 can include such other componentssuitable for use in a system for removing tissue from a passageway inthe body.

Descriptions of some examples of such RAD devices can be found in U.S.Pat. Nos. 5,897,566; 6,024,749; 6,077,282; 6,129,734; and 6,132,444issued to Shturman, each of which is incorporated herein by reference inits entirety; and in U.S. Pat. Nos. 4,990,134 and 5,314,407 issued toAuth.

As shown in FIG. 2, the RAD 20 can include a prime mover carriage 18 anda drive shaft cartridge 16. A fluid supply line 22, a prime mover speedmonitoring line 23, and a gas supply line 24 are adapted to be connectedor coupled to the RAD 20. In one embodiment, the lines 22, 23 and 24 canbe a physical part of and extend from the RAD 20. In an alternateembodiment, the RAD 20 could include one or more couplings or connectionports to allow one or more of the lines 22, 23 or 24 to be connected tothe RAD. Any one of the lines 22, 23 or 24 could be separate from theRAD 20.

Extending from one end of the RAD 20 is an elongated tube 28. Theelongated tube 28 can include a rotatable flexible drive shaft 25 thathas a tissue removal implement 27 located near the distal end of theflexible drive shaft 25. The elongated tube 28 can also include an innerlumen (not shown) between an interior surface of the elongated tube andthe drive shaft 25 along or around which fluid can flow at any suitableor desired rate of flow.

A control knob 21 operatively secured to the prime mover carriage 18 isadapted to facilitate advancing and retracting the prime mover carriage18 with respect to the housing 12 of the RAD 20.

The prime mover carriage 18 generally carries a prime mover (not shown).Preferably, the prime mover is a compressed gas driven turbine, and forpurposes of this description, will be referred to herein as a gasturbine. It should be understood however, that any suitable device canbe used to rotate the drive shaft 25 at a desired rotational speed. Forexample, an electrically powered motor could be used. The gas turbinemay be powered, for example, by compressed nitrogen or compressed airsupplied from system 40. The system 40 usually includes a tank 41 withcompressed gas and a pressure regulator 42.

As shown in FIG. 2, the RAD 20 includes a drive shaft cartridge 16 thatincludes the elongated tube 28 extending distally from the drive shaftcartridge 16. The rotatable flexible drive shaft 25 is generallydisposed within the elongated tube 28. The flexible drive shaft 25 maybe rotated over a guide wire 26. A distal portion of the drive shaft 25may extend distally from the elongated tube 28 and may include thetissue removal implement 27.

Referring to FIG. 2, the RAD 20 can be coupled to the controller 60through one or more connections, including for example a fluid supplyconnection, a gas supply connection and a turbine speed monitoring lineconnection. Fluid is supplied to the drive shaft cartridge 16 from thefluid supply 50 through a fluid supply line 22. As shown in FIG. 2, thefluid supply line 22 is comprised of more than one sequentiallyconnected fluid lines. In alternate embodiments a single line, or anysuitable combination of fluid lines may be used. For example, referringto FIG. 2, a short fluid supply line 54 extends from the drive shaftcartridge 16 and is coupled to a longer fluid supply line 22 with a luerlock device 52. The fluid line 54 is connected or coupled to the innerlumen of the elongated tube 28. In an alternate embodiment, the driveshaft cartridge 16 could include a fitting or coupling to which thefluid supply line 22 can be directly connected. In this manner a fluid,such as for example saline, is supplied to the inner lumen of theelongated tube 28 from the fluid supply 50. The fluid supply line 22could also comprise one or more parallel fluid lines to couple the fluidsupply(s) to the inner lumen(s) of the elongated tube 28.

One or more prime mover speed monitoring lines 23 may be used to monitorthe rotational speed of the gas turbine. For example, in one embodimentthe line 23 could comprise a fiber optic line that is adapted to couplepulses of light from an element of an optical tachometer (not shown) ofthe RAD 20 to the controller 60. The number of such pulses per unit oftime can be used to determine a rotational speed of the gas turbine. Inan alternate embodiment any suitable device can be used to communicatethe rotational speed of the gas turbine of the RAD 20 to the controller60.

The gas supply line 24 is used to provide a compressed gas to the guidewire brake (not shown) and further via gas supply line 29 to the primemover carriage 18 to power the prime mover or gas turbine. As shown inFIG. 2, the gas supply system 40 is a compressed gas system that canprovide a steady flow of gas to the controller 60. Generally, anyconventional or suitable system 40 can be used to supply the flow ofcompressed gas via a gas line 43 to the controller 60. As shown in FIG.2, the compressed gas system 40 comprises one or more tanks or bottles41 coupled to a regulator device 42. In an alternate embodiment, the gassystem could comprise a hospital gas system where the supply ofcompressed gas is generally delivered via a compressed gas line 43 tothe controller unit 60.

As shown in FIG. 2, the system 10 can also include a fluid pump 70. Thefluid pump 70 is generally adapted to pump the fluid from the fluidsupply 50 through the fluid supply line 22 to an inner lumen(s) of theelongated tube 28 and to some other moving parts of the RAD. Althoughthe elongated tube 28 is referred to herein as generally having a lumen,in alternate embodiments, the elongated tube 28 could also include aplurality of lumens.

The speed at which the pump 70 pumps the fluid is generally variable andcontrolled through the controller 60. In the preferred embodiment, thepump 70 comprises a peristaltic (roller) pump. An example of oneembodiment of a peristaltic pump is shown in FIGS. 3-5. As shown in FIG.3, a portion 82 of the fluid supply line 22 is passed through the pump70 and around an outer edge of rollers 80. The tubing portion 82, alsoreferred to herein as the tube or tubing 82, of the fluid supply line 22is generally different from the remainder of the fluid supply line 22and comprises a tube that has special mechanical properties that allowthe tubing to be used within the roller portion of the fluid pump 70. Inone embodiment, the tubing 82 can be made from Tygon.®. LFL tubing or atubing with similar mechanical properties. One type of tubing suitablefor use with peristaltic (roller) pump(s) is commercially available fromthe Plastron, a Tekni-Plex Co., City of Industry, Calif. In oneembodiment, the length of the tubing 82 can be approximately 300millimeters, although any suitable length can be used.

In FIG. 3, the pump handle 75 is in an upward position and the pumpcover 74 is open. In the open position, the rollers 80 do not applypressure to the tube 82. When the handle 75 is moved downward, or into aclosed position as shown in FIGS. 4 and 5, the pump rollers 80 applypressure, or squeeze the tube 82. As the pump motor rotates as shown inFIG. 5, the rollers 80 rotate and force fluid 84 in the tube 82 to bepumped through the fluid line 22. Although the fluid pump 70 shown inFIGS. 3-5 has four rollers, any suitable number of rollers 80 can beused to provide a desired, relatively steady fluid flow. In thepreferred embodiment, the pump 70 has 6 rollers in order to reduce theamplitude of fluid pulsations in the fluid line 22. One example of aroller pump that can be used in one embodiment of the present inventionis roller pump model number 900-1021 manufactured by the BarnantCompany, Barrington, Ill. In the preferred embodiment of the invention,the roller pump can be powered by an electric motor model number 118752and planetary gearhead model number 110396, commercially available fromMaxon Precision Motors, Burlingame, Calif.

Referring to FIGS. 2-6, in one embodiment, a fluid supply line securingdevice 90 can be used to keep the tubing portion 82 of the fluid supplyline from being pulled through the roller pump when the pump 70 isoperating.

As shown in FIG. 6, the fluid supply line securing device 90 generallycomprises a receiving member 92 that at least partially surrounds tube82 and prevents tube 82 from being pulled through the roller pump. Theouter surface of the tube 82 can be bonded in any suitable manner, suchas for example gluing, to an inner surface of a generally tubularchannel of the receiving member 92.

Referring to FIG. 6, in one embodiment, a generally hollow sleeve 94 canbe adapted to be inserted into a proximal portion of the tube 82. Anouter diameter of the sleeve 94 is generally larger than an innerdiameter of the tube 82 so that a portion of the tube 82 around thesleeve 94 is distended when the sleeve 94 is inserted into the tube 82.The portion of the tube 82 around the sleeve 94 becomes wedged againstthe shoulder 98 formed in the tubular channel of the receiving member 92and prevents the proximal portion of the tube 82 from being pulledthrough the receiving member 92.

As shown in FIG. 6, appropriate placement of the tube 82 within thefluid pump 70 requires that a distal end section 96 of the receivingmember 92 becomes abutted against a corresponding surface 93 of a fluidpump housing 97. This prevents the receiving member 92 and the tube 82from being pulled through the fluid pump when the rollers 80 arerotating.

Although as shown in FIG. 2, the pump 70 is shown as integrated into thecontroller 60, it should be understood that the pump 70 could also belocated externally to the controller 60, and comprise for example, astand alone fluid pumping system. In an alternate embodiment, anysuitable device for pumping fluid can be used, such as for example, acentrifugal pump or syringe type device. It is a feature of the presentinvention to be able to provide a variable and/or regulated flow offluid through the inner lumen of elongated tube 28 during the operationof the system 10.

As shown in FIG. 2, in one embodiment, the fluid supply system 50 cancomprise a fluid bag connected to a drip chamber 52 that is connected tothe fluid line 22. The fluid supply line 22 can generally comprise oneor more sections of fluid supply tubing that can be coupled together inany suitable manner. As discussed above, in the preferred embodiment,the fluid supply line 22 includes a tubing portion 82 that has specialmechanical properties suitable for use with a peristaltic (roller) pump.Preferably, the tubing portion 82 is not only made from a material thathas special mechanical properties different from the rest of the fluidsupply line 22, but also has inner and/or outer diameters that aredifferent from the inner and/or outer diameters of the rest of the fluidsupply line 22.

The system 10 also includes the activation device 30 that is coupled tothe controller 60 via control line or lines 36. Although as shown inFIG. 2, line 36 is a single line, it should be understood that in thepreferred embodiment, the line 36 comprises a cable that includes one ormore electrical or fiberoptic lines 36. In an alternate embodiment, theline 36 could include pneumatic or other suitable types of communicationlines. The activation device 30 is generally adapted to control oractivate an increased flow rate of fluid from or through the pump 70.The activation device 30 can also be used to control the activation ofthe gas turbine of the RAD. Generally, the activation device 30 is aswitching device having “ON” and “OFF” positions. In one embodiment asshown in FIG. 2, the activation device 30 comprises a pair of pedalswitches, a pump pedal 32 and a turbine pedal 34. In a preferredembodiment, pedal switches 32 and 34 are electrical switches and controlline 36 comprises an electrical cable with more than one wire therein,each wire adapted to carry electrical or communication signals. It is afeature of the present invention to allow an operator of the RAD 20 toincrease the speed of the pump 70 or activate the gas turbine using thefoot pedals 32 and 34 shown in FIG. 2, or a single foot switch 1101 asshown in FIG. 26.

In an alternate embodiment any suitable switching or control device canbe used other than a pedal activated switch to provide an “ON” or “OFF”activation signal. For example, as shown in FIGS. 25 and 26, a singlepedal switch 1010 or 1101 and control systems 1000 or 1100, may beutilized in such a fashion so that a first activation of the switch (thefirst pulse or the first control signal) causes the fluid pump 70 toincrease its speed of rotation, then the second activation of the switch(the second pulse or the second control signal) causes the fluid pump 70to continue to rotate at the increased speed and activates the gasturbine, and finally, the third activation of the switch (the thirdpulse or the third control signal) turns off both the gas turbine and(after a delay if needed) the fluid pump 70, bringing the entire systemto its “steady-state” or “static” mode. For example, in such static modethe fluid pump 70 returns to it minimum or “min” fluid flow rate and thegas turbine is turned “OFF.”.

The controller 60 shown in FIG. 2 is generally adapted to control andmonitor the operations of the system 10, including the fluid flow rateand gas turbine function and speed. The controller 60 can includedisplays 61, 63, 64, 65 and 66 to monitor compressed gas pressureapplied to the gas turbine of the RAD, turbine rotational speed, variousprocedure time intervals, and other functions of the system 10, controlsand switches 62, 67 and 68 to operate the various functions of thesystem 10 as well as connections to each of the components of the system10. The controller 60 will also include the electronics and circuitryneeded to operate the system 10.

For example, as shown in FIG. 2, display 65 can comprise an “individual”event timer adapted to display and/or record the length of time duringwhich the turbine was rotating after each individual activation(“individual event time”). Display 66 can comprise a “procedure timer”that displays the sum of the individual event times, i.e. the total timeduring which the gas turbine was operational throughout the angioplastyprocedure. Each of the displays can include a reset button to reset thetime. For example, the “procedure timer” may be used to record a totaltime used to completely open the stenotic lesion and then reset back to“zero.” Display 63 can be used to display a rotational speed of theturbine 19. In an alternate embodiment, any suitable number or types ofdisplays can be used for indicating the functions and events of thesystem 10.

Referring to FIG. 7, a block diagram illustrating the functional aspectsof one embodiment of the controller 60 is shown. With reference to FIGS.2 and 7, the controller 60 can be used to control the activation andspeed of the pump 70, the activation and speed of the gas turbine of theRAD and, for these purposes, can include a fluid pump control unit 610and a pneumatic valve control unit 650.

The pump control unit 610 is generally adapted to control the speed of afluid pump motor 612 in order to regulate the flow rate of fluid throughthe inner lumen of the, catheter 28. The fluid pump motor 612 is alsoshown in FIGS. 13 and 14 as a fluid pump motor 1612. The controller 60can include a minimum pump speed setting control or device 621, whichcan be adjusted to set the minimum fluid flow rate or speed of the pumpmotor 612 when the gas turbine and the drive shaft 25 of the RAD are notrotating, for example. The maximum pump speed setting control or device622 can be adjusted to set a maximum fluid flow rate, or the maximumspeed of the pump motor 612.

When electric power is applied to the controller 60, the pump controlunit 610 can set the pump motor 612 to operate in a “steady-state” or“static” mode. In this static mode the gas turbine and the drive shaft25 are generally not rotating and minimal flow rate of fluid ismaintained. When, for example, the fluid pump control switch 632 (whichis similar to pedal switch 32 in FIG. 2) is activated, the pump controlunit 610 can send a signal to the pump motor 612 to increase its speed.The increase of the speed of the pump motor 612 will increase the fluidflow rate.

The pneumatic valve control unit 650 generally controls the operation ofthe gas turbine 605 of the RAD. When the turbine control switch 634(similar to pedal switch 34 in FIG. 2) is activated the pneumatic valvecontrol unit 650 sends a signal to activate the turbine pneumatic valve657, which allows compressed gas from the turbine pressure regulator 658to be applied to the gas turbine 605 of the RAD. The fluid pump controlunit 610 also communicates with the pneumatic valve control unit 650 tocoordinate operation of the fluid pump 70 with the gas turbine of theRAD. It is a feature of the present invention that the turbine controlswitch 634 needs to be activated within a predetermined time periodafter the fluid pump control switch 632 is deactivated in order toactivate the gas turbine of the RAD. If the turbine control switch 634is not activated within the predetermined time period after deactivationof the fluid control switch 632, operation of the gas turbine of the RADcan be either prevented or delayed. In one embodiment, when the turbinecontrol switch 634 is activated before activation of the pump controlswitch 632, of after the expiration of the predetermined time period,operation of the gas turbine of the RAD will be delayed for anotherpredetermined time period after activation of turbine control switch 634during which time the fluid pump 70 is pumping fluid at an increased ormaximum speed.

The turbine pressure regulator 658 could comprise a Precision LowPressure Regulator, Type LPR-¼-4, commercially available from FESTOCorporation, Hauppauge, N.Y. The turbine pneumatic valve 657 couldcomprise a single solenoid valve type MFM-5-⅛-S-B, also available fromthe FESTO Corporation.

Compressed gas pressure at the output of the turbine pressure regulator658 is measured and displayed by the turbine pressure sensor and displaydevice 671, (which is similar to the turbine pressure display device 61in FIG. 2). Both turbine pressure sensor 671 and turbine tachometer 668may be in communication with the pneumatic valve control unit 650, whichmay be programmed to turn off or deactivate the turbine pneumatic valve657 if a discrepancy of predetermined magnitude develops betweenpressure applied to the gas turbine 605 and the rotational speed of theturbine.

When the gas turbine of the RAD is activated, the controller 60 caninclude an “individual” event time indicator 655 (display 65 in FIG. 2)that indicates the length of time during which the turbine was rotatingafter each individual activation. A “procedure” time indicator 666(display 66 in FIG. 2) can be used to display a total time during whichthe gas turbine was operational throughout the angioplasty procedure orpart thereof.

The pneumatic valve control unit 650 could also provide data storageand/or output signal(s) 654 that could be used to plot the operation ofthe gas turbine and other components of the system 10. For example, thedata storage and/or output signal(s) 654 could be fed to a logger orchart recorder in order to plot the time and functions of the gasturbine 605, fluid pump 70 and other elements of the controller 60, suchas for example, gas pressure applied to the gas turbine and itsrotational speed, under such pressure, may be logged.

During a rotational angioplasty procedure a fluid such as saline ispumped from the fluid supply 50 through the elongated tube 28. When thegas turbine of the RAD is activated the drive shaft 25 is rotated at ahigh speed. The turbine block 18 can be moved forward and/or backwardwith respect to the housing 12 of the RAD 20 thereby allowing theoperator to move the drive shaft 25 and its abrasive element 27 forwardand/or backward across the stenotic lesion. Generally, in the presentinvention, when the drive shaft 25 is rotating, saline is being pumpedfrom or through the pump 70 at a higher rate of flow than when the driveshaft 25 is not rotating. The increased flow of saline can provide,among other things, enhanced cooling of the treated area andsubstantially uninterrupted flushing away of the small particlesgenerated as the stenotic material is removed by the abrasive element27. Saline is pumped through the elongated tube 28 at a minimal flowrate when the system 10 is in a static state and the drive shaft 25 isnot rotating.

In the present invention, the controller 60 and the activation device 30are adapted to “delay” activation of the gas turbine of the RAD toprovide a “preflush” of saline prior to initiating “active” rotation ofthe gas turbine. The term “preflush” as used herein describes pumping ofsaline through the elongated tube 28 at an increased flow rate. Forexample, referring to FIG. 8, at time t.sub.o, the gas turbine,represented by its rotational speed .omega, is off, and the saline flowrate Q is at flow rate Q.sub.1. In one embodiment flow rate Q.sub.1could be at a minimum or “min” level when the system 10 is in a staticmode. Upon activation of switch 32, the saline flow rate Q increasesfrom flow rate Q.sub.1 to Q.sub.2. Saline flow rate Q.sub.2 is a higherflow rate than Q.sub.1, being for example, a maximum or “max” flow rate.The gas turbine remains off. It should be understood that although thesaline flow rate Q.sub.2 is shown as increasing to the “max” uponactivation of pedal switch 32, any suitable flow rate Q.sub.2 can beused. At time t.sub.2, the pedal switch 32 is deactivated, or is “OFF.”The saline flow rate remains at increased flow rate Q.sub.2 for a periodof time shown as t.sub.delay. In FIG. 8 this t.sub.delay time periodcorresponds to the time period between t.sub.2 and t.sub.5. A period oftime between t.sub.1 and t.sub.2, together with that period of timewithin t.sub.delay during which saline flow is maintained at anincreased flow rate prior to activation of the gas turbine, is referredto herein as the “preflush time period.” The drive shaft 25 and itsabrasive element 27 are not rotating during the preflush time period.

The preflush time period prior to activation of the drive shaft 25provides several advantages. Some of these advantages can include forexample, flushing both the abrasive element 27 and the stenotic area tobe treated with saline that can include a suitable concentration ofheparin and other pharmaceuticals that can prevent platelet aggregationand thrombus formation. The dilution of the blood that flows through thearea of treatment and around the abrasive element may be sufficient tosignificantly reduce the potential for platelet activation, plateletaggregation and thrombus formation. Dilution or even hydrolic occlusionof blood flow through the area of treatment may also reduce the numberof red blood cells in the treatment area and or around the abrasiveelement 27 of the drive shaft 25, and, therefore, prevent hemolysis ofthe red blood cells at the time when the drive shaft 25 and its abrasiveelement 27 begin and continue to rotate. In general, the “preflush” flowof fluid to the site of the tissue removal prior to the turbineactivation provides a more favorable environment for the rotationalangioplasty procedure.

It is a feature of the present invention to provide a preflush timeperiod so that activation of the gas turbine of the RAD is prevented orprecluded without a continuous preflush time period. In the presentinvention, the acceleration of the saline flow rate is substantiallyindependent from rotation of the gas turbine and drive shaft 25 of theRAD 20. For example, referring to FIG. 9, at time t.sub.4, the turbinepedal switch 34 is activated or is “ON.” This activation of switch 34instructs the controller 60 to activate the gas turbine of the RAD 20and initiate rotation of the gas turbine and drive shaft 25. Since theactivation of switch 34 occurs at time t.sub.4 and within the timeperiod t.sub.delay, the gas turbine of the RAD is activated. As shown inFIG. 9, the saline flow rate Q remains at increased flow rate Q.sub.2during at least the time period t.sub.4 to t.sub.7 when the gas turbineis “ON” or rotating.

Referring to FIG. 10, the t.sub.delay time period can be extended orrepeated by reactivating the fluid pump pedal switch 32. For example, attime t.sub.o, the gas turbine is “OFF” and the fluid flow rate is atQ.sub.1. At time t.sub.1, fluid pump pedal switch 32 is activated,which, as shown in FIG. 10, is represented as a depression of pump pedalswitch 32.

Activation of the fluid pump switch 32 causes the saline flow rate Q toincrease from Q.sub.1 to Q.sub.2. At time t.sub.2, pump pedal switch 32is released or deactivated and the fluid flow remains at increased flowrate Q.sub.2. The saline flow rate shall remain at increased saline flowrate Q.sub.2 for the t.sub.delay period, shown as from time t.sub.2 totime t.sub.5. As shown in FIG. 10, at the time t.sub.3 (before the endof the time period t.sub.delay) fluid pump pedal switch 32 has beenactivated for a time period t.sub.3 to t.sub.4. At the time t.sub.4,when the fluid pump pedal switch 32 is deactivated, the time periodt.sub.delay starts again, running from time t.sub.4 to t.sub.8. It is afeature of the present invention that this “preflush” or preflush timeperiod can be executed or extended as many times as desired by theoperator of the system 10.

Referring to FIG. 9, if the turbine pedal switch 34 is activated duringthe t.sub.delay time period, the gas turbine switches “ON.” For example,as shown in FIG. 9, at time t.sub.2, the fluid pump pedal switch 32 isdeactivated and the t.sub.delay time period starts, with the fluid flowrate remaining at the increased flow rate Q.sub.2. At time t.sub.4, orbefore the time period t.sub.delay has expired, the turbine pedal switch34 is activated. The gas turbine goes from “OFF” to “ON” and the salineflow rate remains at the increased flow rate Q.sub.2. At time t.sub.7the gas turbine is switched “OFF” by the release of turbine pedal switch34. In one embodiment, as shown in FIG. 9, the saline flow rate Q canremain at the increased level Q.sub.2 for another delay time period fromtime t.sub.7 to time t.sub.9 as represented by t.sub.delay’. In analternate embodiment, the fluid flow rate could go from Q.sub.2 toQ.sub.1 at time t.sub.7. It is a feature of the present invention toprovide a “postflush” or “postflush time period” of accelerated orincreased fluid flow rate after the gas turbine and drive shaft 25 stoprotating. The time period for t.sub.delay or t.sub.delay, can be anysuitable or desired time period. The t.sub.delay and t.sub.delay’, timeperiods may comprise time periods of different length.

Referring to FIG. 11, if the turbine pedal switch 34 is activated at anytime t.sub.6 after the time period t.sub.delay has expired at the timet.sub.5, then the controller 60 could prevent the turbine fromactivating. If the gas turbine of the RAD 20 has not been activatedduring an uninterrupted preflush time period as shown in FIG. 11, thenthe controller 60 may also be designed or programmed to switch the fluidpump 70 into the “preflush” mode upon activation of the turbine pedalswitch 34 and activate the gas turbine of the RAD 20 only after apredetermined preflush time period has expired. It is a feature of thepresent invention to provide an increased level of fluid flow through anelongated tube 28, and around the drive shaft and through the stenotictreatment area prior to rotation of the drive shaft 25.

The fluid pump 70 is not powered by or brought into motion by the gasturbine or any other prime mover of the RAD and therefore anacceleration of the fluid flow around the driveshaft 25 is only modestlyaffected by the rapid rotation of the drive shaft, which when rapidlyrotated can act as a screw pump. In the preferred embodiment the rapidrotation of the drive shaft 25 causes about a 30% decrease inaccelerated fluid flow rate when compared to accelerated fluid flow ratearound a non-rotating drive shaft.

Referring to FIG. 12A, a timing circuit 200 could be used to provide thet.sub.delay time period after deactivation of the pump pedal switch 32in the embodiment(s) of the invention shown in FIG. 2 and FIGS. 7-11.

Switch 232 of the timing circuit 200 remains “open” for as long as thepump pedal switch 32 is not activated. During that time period voltageacross the capacitor C.sub.1 is equal to the voltage across capacitorC.sub.2 (voltages at inputs 5 and 7 of the Digital Circuit NE 555 areequal) and a control signal U.sub.out out is 0 (zero). Activation ofpedal switch 32 at the time t.sub.1 in FIG. 8, for example, will “close”switch 232 thereby causing immediate discharge of the capacitor C.sub.1through the transistor Q.sub.2. The control signal U.sub.out of theDigital Circuit NE 555 will immediately change from 0 to 1.

At the time t.sub.2 in FIG. 8, for example, when the fluid pump pedal 32is released and switch 232 opens, the capacitor C.sub.1 charges and theDigital Circuit NE 555 provides control signal U.sub.out equal to 1until the capacitor C.sub.1 is fully charged. Therefore the fluid pump70 continues to pump fluid at an accelerated or increased fluid flowrate only for as long as the control signal U.sub.out remains at 1.

At the time t.sub.5 in FIG. 8, when the capacitor C.sub.1 of the timingcircuit 200 becomes fully charged (voltages at the inputs 7 and 5 becomeequal), the control signal U.sub.out will change from 1 to 0, therebycausing the fluid pump 70 to return to pumping fluid at the minimum or“min” fluid flow rate.

The t.sub.delay time period shown in FIGS. 8-11 is defined by a chargetime of the capacitor C.sub.1, in the timing circuit 200. The chargetime of the capacitor C.sub.1, and the t.sub.delay time period shown inFIGS. 8-11 may be adjusted within certain limits by the potentiometerR.sub.2 in the timing circuit 200.

A separate timing circuit similar to the timing circuit 200 can be usedwith the turbine pedal switch 34 in order to provide the t.sub.delay’time period and “postflush” of accelerated flow of fluid after theturbine pedal switch 34 is released.

As shown in FIG. 12B a single timing circuit 210 may provide equalt.sub.delay and t.sub.delay’ time periods. This is accomplished byconnecting in parallel switches 232 and 234, which correspond to pedalswitches 32 and 34 in FIG. 2 and FIGS. 8-11.

The controller 60 could also include one or more safety devices tomonitor proper operation of the system 10. For example, in oneembodiment as shown in FIG. 7, the controller 60 could include a pumpcover sensor 624. The pump cover sensor 624 could indicate whether thepump cover 74 shown in FIG. 2 is in an open or closed position. Forexample, as shown in FIG. 4, when the pump handle 75 is in a “DOWN”position, the pump cover sensor 624 can provide the pump control unit610 with a suitable signal which allows the pump control unit 610 toactivate the pump motor 612. If the pump cover 74 is “OPEN”, asindicated by the pump cover handle 75 being in an “UP” position as shownin FIG. 3, pump cover sensor 624 will either not provide the signal thatis needed to activate the pump motor 612 or can generate a signal thatprevents the pump motor from being activated. Therefore, when the pumpcover 74 is “OPEN”, operation of the pump motor 612 can be prevented orinterrupted.

In one embodiment as shown in FIGS. 13 and 14 the pump cover sensor 624could comprise a switch device 310 adapted to detect a closed or openposition of the pump cover 74. For example, as shown in FIG. 13 when thepump handle 75 is an “UP” position, the pump cover 74 is in an “OPEN”position. In FIG. 14 when the pump handle 75 is “DOWN”, the pump cover74 is “CLOSED.” In the preferred embodiment, the switch 310 couldcomprise a magnetically operated sealed switch that uses a magnet 312 topreferably determine a “CLOSED” position of the pump cover 74. Such aswitch, also called a reed switch, is commercially available fromPremier Farnell plc of Chicago, Ill. In an alternate embodiment, anysuitable device or switch can be used to determine an “OPEN” or “CLOSED”position of the pump cover 74, such as for example, a Hall effectswitch, an optical switch, a mechanical switch or a limit switch.

As shown in FIG. 7, a fluid alarm unit 630 could be used to provide anaudible and/or visual warning of the pump cover condition. For example,when the pump cover 74 is open, an audible alarm device 682 and/or avisual alarm device 684 can be activated to warn the user of thecondition. An indicator 64 of the controller 60 shown in FIG. 2 could beused to display the visual warning. An audible alarm or verbal warningmay be provided via siren or speaker 69 shown in FIG. 2.

As shown in FIG. 7 the controller 60 could also include a fluid levelsensor 626. The fluid level sensor 626 could be used to detect a lowlevel of fluid in the fluid supply system 50. The fluid level sensor 626is in communication with both the fluid pump control unit 610 and thefluid alarm unit 630. If during an angioplasty procedure the fluid levelin the saline bag 50 reaches a predetermined low level, then a fluidalarm unit 630 can activate visual and audible alarm devices 684 and 682in order to warn or advice the operator of the system 10 of thecondition. The controller 60 could also include an alarm mute device 636that can allow the user to silence or mute the audible alarm device 682for a predetermined period of time or a predetermined number ofrevolutions of the pump motor 612. Furthermore, in one embodiment of theinvention, operation of the pump motor 612 and/or the gas turbine couldbe prevented or stopped if the fluid level sensor 626 detects apredetermined low level of fluid in the saline bag of the fluid supply50. If the pump motor 612 is operating and the fluid sensor 626 detectsa low fluid level, in one embodiment the fluid alarm unit 630 couldactivate the visual alarm device 684 and/or provide a verbal warning oractivate audible alarm device 682 to indicate the situation to the user.The alarm mute device 636 can allow the user to silence the alarm 682and continue the procedure. The visual alarm 684 could remain active.The controller 60 could also be adapted to reactivate the audible alarm682 after it was silenced if a predetermined time period elapses or ifthe fluid pump 70 or pump motor makes a predetermined number ofrevolutions or if the fluid level reaches a next predetermined lowlevel. This process could continue for as long as the operator desiresor until a predetermined minimum level of fluid is reached. Thecontroller 60 could also include a fluid pump blocking control switch625, that when activated, could prevent operation of the fluid pumpmotor 612. Referring to FIG. 2, in one embodiment of the presentinvention, a push button 82 can be used to silence the audible alarmdevice 69 and push button 68 to operate the pump blocking control ordevice 625 shown in FIG. 7. In the preferred embodiment of the inventionpush button 68 comprises a pushbutton switch with a red screen. If anoperator of the controller 60 activates push button 68 (prevents orstops operation of the fluid pump 70), then red screen of the pushbuttonswitch becomes illuminated by a filament or LED lamp.

The pushbutton switches of the type used in the preferred embodiment ofthis invention are commercially available from Apem Components, Inc. ofWakefield, Mass.

Referring to FIGS. 15 and 16, one embodiment of a fluid level detectionsystem 300 is shown. In FIG. 2, the fluid container 50 is suspended froma mounting pole or member 302. One end of the pole 302 is inserted intoa receptacle 304. As shown in FIG. 15, the lower end of the pole member302 comes to rest against a horizontal beam member 310. The beam member310 is adapted to pivot around a point (not shown). In one embodiment,one end 312 of the beam member 310 is adapted to move in a downwarddirection as the combined weight of the fluid bag 50 and the pole member302 bears down on the end 312 of the beam member 310. The combinedweight or force exerted by the fluid bag 50 and the pole member 302determines the movement or displacement of the end 312. The other end314 of the beam member 310 is adapted to move in a direction opposite tothe movement of the end 312. A bias element 316, such as for example aspring, can be used to apply to the end 314 a biasing force directed inthe direction opposite to the direction of movement of the end 314 ofthe beam member 310. Compressing the bias element 316 using a bolt orscrew type device 320 can increase the tension of the bias element 316and the force that the bias element 316 exerts on the end 314. Forexample, as shown in FIG. 15, a bolt 320 is inserted into a block 318and as the bolt 320 is turned, the block 318 moves in a downwarddirection compressing the spring 316 and increasing its tension. Theincreased tension of the spring 316 increases the biasing force appliedto the end 314. In operation, when a full saline bag is placed on thepole 302, the end 312 is forced by the combined weight of the bag 50 andpole 302 to deflect downward a certain distance. As the fluid in the bag50 is depleted, the weight of the fluid bag 50 decreases and the end 312moves in an upward direction while the end 314 moves downward. As shownin FIG. 16, when the fluid level in the saline bag 50 reaches apredetermined level, the end 314 of beam member 310 comes in contactwith a switch device 322. The contact of the member 314 with the switchdevice 322 can cause the fluid alarm unit 630, shown in FIG. 7, toactivate visual and audible alarm devices 684 and 682. In an alternateembodiment, any suitable device or mechanism can be used to monitor thefluid level in the saline bag. It is a feature of the present inventionto provide a warning to the operator of the system 10 that the fluidlevel in the fluid supply 50 has reached a predetermined low level.

FIGS. 17 and 18 show another embodiment of a fluid level detectionsystem 800. In this embodiment, the pole member 302 rests on a rod 824that activates switch device 822 when the fluid level in the fluidsupply 50 is above a predetermined low level. As the fluid leveldecreases and reaches a predetermined level, a spring 830 or otherbiasing element starts to move rod 824 in an upward direction. As shownin FIG. 18, when the fluid level in the fluid bag 50 reaches apredetermined low level, rod 824 gets out of contact with anddeactivates switch 822, thereby causing fluid alarm unit 630, shown inFIG. 7, to activate visual alarm device 634 and audible alarm 932.

In the preferred embodiment, audible alarm device 682 is activated witha certain predetermined delay with respect to the visual alarm device684. Such a sequence of alarms is advantageous in order to limit anydisturbance to the patient.

FIGS. 19 and 20 show yet another embodiment of a fluid level detectionsystem 850. In this embodiment a biasing element or spring 852 isdisposed around the lower portion of the pole 854. In operation, when afull saline bag 50 is placed on the pole 854, the biasing element 852becomes compressed between a shoulder 850 of the pole 854 and anadjustment element or screw 857. The combined weight of the full bag 50and the pole itself will force the lower end of the pole against aswitch device 858, thereby providing for direct activation of the switchdevice 858 by the lower end of the pole.

As shown in FIG. 20, when the fluid level in the bag 50 reaches apredetermined low level, the biasing spring 852 moves the pole 854 in anupward direction, thereby deactivating switch device 858 and causingfluid alarm unit to activate visual and audible alarms.

FIGS. 21 and 22 show yet another embodiment of a fluid detection system860 in which a tensiometer device 862 is utilized instead of a switchdevice. The tensiometer device measures the pressure applied to thedevice and generates a corresponding electrical signal. A spring typedevice incorporating e.g. spring 864 can be used to dampen the impact ofthe pole 866 against the tensiometer device 862 in order to preventdamage to the tensiometer device. However, as shown in FIG. 23, the pole867 of a modified fluid level detection system 860′ can directly contactthe tensiometer device 862. In one embodiment, the tensiometer device862 can include internal mechanisms to dampen the impact on of the poleon the tensiometer device, when, for example, a fluid bag 50 is placedon the pole 867.

As shown in FIG. 7, the controller 60 could also include an inputcompressed gas pressure sensor(s) combined with a compressed gas shutoffvalve(s) 670. In the preferred embodiment, the shutoff valve 670 isgenerally adapted to shut off the compressed gas supply to the turbinepressure regulator or the controller 60 when the input compressed gaspressure from the system pressure regulator 42 of the compressed gassource 40 exceeds a predetermined level. An additional pressure sensorcombined with its own low pressure shutoff valve may be adapted to shutoff the compressed gas supply to the turbine pressure regulator 658 orthe controller 60 when the input gas pressure is at or below apredetermined level. In addition, input pressure sensors may generate asignal to the pneumatic valve control unit 650 that preclude activationof the turbine pneumatic valve 657 and therefore, the gas turbine 605 ofthe RAD. The signal from the input pressure sensor(s) may also activatea visual and/or audible alarm device, either directly or indirectly viathe pneumatic valve control unit 650. The gas pressure alarm device orgas pressure alarm(s) 673 may be programmed to warn about the input gaspressure being or becoming either too high or too low. Input compressedgas pressure that does not exceed a predetermined upper level, or iswithin a predetermined range between upper and lower levels is suppliedto the turbine pressure regulator 658. A control knob 62 of the turbinepressure regulator 658 is shown in FIG. 2 and can be used to adjust thegas pressure applied to the gas turbine of the RAD.

A turbine pressure sensor and turbine pressure display device 671 can beused to display the gas pressure applied to the gas turbine. The turbinepressure sensor and the turbine pressure display device 671 can becombined into one device, such as for example an analog pressure gauge61 as shown in FIG. 2. Although the gauge 61 shown in FIG. 2 isillustrated as an analog device, any suitable indicator can be used,such as for example a digital display. In an alternate embodiment, thepressure could be displayed on a system other than the controller 60,such as for example an external display or monitor.

The rotational speed of the gas turbine of the RAD shown in FIG. 2 canbe monitored by a turbine tachometer 668 shown in FIG. 7. In thepreferred embodiment an improved optical tachometer for the RAD, such asthat described in U.S. Pat. No. 6,039,747 to Shturman can be used.Referring to FIG. 2, in the preferred embodiment, the optical tachometer63 utilizes only one optical fiber 23 to conduct both uninterruptedlight from the controller 60 to the RAD 20 and pulsed light back to thecontroller 60. In the rotational angioplasty system of the prior art,shown in FIG. 1 and described in U.S. Pat. No. 5,314,407 to Auth theturbine optical tachometer utilizes two optical fibers. The controller60 of the present invention can be adapted to interface with thisturbine tachometer of the prior art. In an alternative embodiment, anysuitable device can be used to monitor the rotational speed of theturbine, including for example optical, electro-optical, electromagneticand acoustic tachometers can be used.

As shown in FIG. 2, the rotational speed of the turbine of the RAD canbe displayed on a turbine tachometer display 63. In the preferredembodiment of the invention, shown in FIG. 2, a digital tachometerdisplay 63 is utilized. In an alternate embodiment, any suitable device,including for example an analog display device, can be used to displaythe rotational speed of the gas turbine of the RAD.

As shown in FIG. 7, in the preferred embodiment, the controller 60 mayalso include a tachometer test device 674 to test for adequate functionof that portion of the turbine tachometer that is located in thecontroller 60. A pushbutton switch could be included on the controller60 for this purpose.

In one embodiment, as shown in FIG. 7, the turbine tachometer 668 can becoupled or connected to the pump control unit 610. The turbinetachometer 668 could provide an input signal to the pump control unit610, thereby causing adjustment of the rotational speed of the fluidpump motor 612 depending on the rotational speed of the gas turbine.

It should be understood that although the switches 32 and 34 in FIG. 2,and similar switches in FIGS. 7 and 24, are shown as two separate pedalactivated switches, any suitable switching device(s) can be used,including a switching device comprising a single switch.

Referring to FIG. 24, one embodiment of a control system 900 forcontrolling fluid pump 904 and gas turbine 305 of rotational angioplastydevice is illustrated. As shown in FIG. 24, a microcontroller 901,receives a combination of inputs comprising U.sub.P1 from pump pedalswitch 932 (which is similar to the fluid pump pedal switch 32 in FIG.2), U.sub.P2 from turbine pedal switch 934 (which is similar to theturbine pedal switch 34 in FIG. 2), and a turbine speed signal U.omega.from a turbine tachometer 902. It should be understood that themicrocontroller based control system shown in FIG. 24 can be programmedto perform substantially all of the functions of the control systemshown in FIGS. 2 and 7. In particular, in one embodiment, themicrocontroller 901 can be programmed to activate a turbine pneumaticvalve 903 only if the fluid pump 904 was activated to pump saline at anaccelerated rate for at least a minimum predetermined period of timeusing the pump pedal switch 932 and if the turbine pedal switch 934 wasactivated within a predetermined time period t.sub.delay after the pumppedal switch 932 has been deactivated.

As shown in FIG. 25, a single pedal activated switch 1010 could be usedto control microcontroller 1001 where a first switch activationestablishes a first mode of operation for the system 1000 (e.g. thefluid pump 1004 is “ON”). A second switch activation establishes asecond mode of operation for the system 1000 (e.g. both the fluid pump1004 and the gas turbine 1005 are “ON” or active). A third switchactivation returns the system to its “static” state where the fluid pumpis at minimum or “min” flow rate and the gas turbine is “OFF.”

An example of a single pedal switch 1101 is shown in FIG. 26. All otherelements of the system 1100 shown in FIG. 26 are similar and have thesame numbers as the elements of the system 10 shown in FIG. 2.

It should be understood that the foregoing description is onlyillustrative of the invention. Various alternatives and modificationscan be devised by those skilled in the art without departing from theinvention. Accordingly, the present invention is intended to embrace allsuch alternatives, modifications and variances which fall within thescope of the appended claims.

1-87. (canceled)
 88. A fluid control system for a rotational atherectomydevice comprising: a fluid pump connected to the atherectomy device; afluid supply connected to the fluid pump; a first control switch adaptedto initiate and maintain a dynamic flow of fluid to the atherectomydevice; and a second control switch adapted to maintain dynamic flow offluid through the atherectomy device and initiate and maintain arotation of a drive shaft in the atherectomy device.
 89. The fluidcontrol system of claim 88, further comprising a control device adaptedto receive inputs from the first control switch and the second controlswitch and regulate a pumping of the fluid by the fluid pump.
 90. Thefluid control system of claim 88, wherein the control device is adaptedto maintain the dynamic flow of fluid for a predetermined time periodafter a deactivation of the first control switch.
 91. The fluid controlsystem of claim 88, wherein the control device is further adapted tomaintain the dynamic flow of fluid and initiate the rotation of thedrive shaft if the second control device is activated within apredetermined time period after a deactivation of the first controldevice.
 92. The fluid control system of claim 88, wherein the controldevice is adapted to prevent the rotation of the drive shaft if thesecond control device is activated after an end of a predetermined timeperiod following a deactivation of the first control device.
 93. Thefluid control system of claim 88, wherein the first control switchcomprises a foot activated switch device.
 94. The fluid control systemof claim 88, wherein the second control switch comprises a footactivated switch device.